A condition known as "Cotard's syndrome" can convince a person that they have become a zombie, ABC News reported.

A man only identified as Graham told New Scientist that he woke up from a suicide attempt in which he tried to electrocute himself in his bathtub and was convinced that he was dead.

"I just felt like my brain didn't exist anymore," Graham told the magazine "I kept on telling the doctors that the tablets weren't going to do me any good, because I didn't have a brain. I'd fried it in the bath."

Graham was diagnosed with Cotard's Syndrome, a phsychiatric condition that causes the person to believe that they are a walking corpse. A 2003 report defined the condition as  "the fixed and unshakable belief that one has lost organs, blood or body parts," according to ABC News.

"I lost my sense of smell and taste. I didn't need to eat, or speak or do anything," Graham said. "I ended up spending time in the graveyard because that was the closest I could get to death."

Little research has been done on the syndrome, except for some case reports dating back to 1882. Scientists were able to study Graham's brain with new technology in order to better understand the condition.

"I've been analyzing PET scans for 15 years, and I've never seen anyone who was on his feet, who was interacting with people, with such an abnormal scan result," said Dr. Steven Laureys of the University of Liège in Belgium, who consulted on Graham's case. "Graham's brain function resembles that of someone during anesthesia or sleep. Seeing this pattern in someone who is awake is quite unique to my knowledge."

Laureys reasoned that Graham's reduced metabolism was giving him "an altered experience of the world and affecting his ability to reason about it."

Graham said that at the time, the fact that he didn't die was a "nightmare." With the help of therapy, medication, and a lot of time, Graham is finally feeling more alive.

"I don't feel that brain-dead anymore," he told New Scientist. "Things just feel a bit bizarre sometimes."

Graham claims that he is not afraid of death, but this has nothing to do with his undead experience. "We're all going to die sometime. I'm just lucky to be alive now," he said.